Methods for locating and routing to target devices' (e.g., mobile or portable radios or subscriber units) communications from sourcing devices (e.g., mail servers, fixed or mobile subscriber units, etc.) in conventional networks are known in the art. For example, via a wired line network, e.g., the internet, a mobile target device must first register with the visited, local communications server to which it is attached before the sourcing device can locate and route communications thereto. Registration with the local communications server is accomplished using a Dynamic Host Configuration Protocol (DHCP), which provides the target device with an Internet Protocol (IP) address for the session. In addition, the target device must advise the local communications server with the IP address of its home communications server. The local communications server then informs the home communications server with the DHCP address of the target device.
For the sourcing device to communicate with the target device, the sourcing device must send a Transmission Control Protocol (TCP) packet addressed to the target device. The home communications server intercepts the TCP packet, prepends the IP address of the local communications server thereto, and forwards the TCP packet to the target device via the local communications server. The local communications server strips the prepended IP address and forwards the TCP packet to the target device.
As this method is performed for each communication packet issued by the sourcing device, the sourcing device never learns of the true location of the target device. Therefore, since no direct connection is achieved between the local communications server to which the target device is attached and the sourcing device, this method suffers the disadvantage of requiring unnecessary communications to and from at least one unneeded network communications server. These extra communications flood the network resulting in a diminution of the bandwidths available to other network users and, accordingly, undesirably reduces the profitability of operating the network. Furthermore, this method is also seen to require the use of additional, prepended addressing which functions to increase the communication packet size. This increase in communication packet size also tends to reduce network efficiency.
Similarly, in a wireless system, e.g., Cellular Digital Packet Data (CDPD) systems, the mobile target device must first register with the visited network Mobile Database System (MDBS) or local communications server to which it is attached before the sourcing device can locate and route communications thereto. Registration with the local communications server is accomplished by the target device using a Mobile Network Registration Protocol (MNRP). The local communications server thereafter notifies its Mobile Data Intermediate System (MD-IS) of the visiting target device for the purpose of registering the target device therewith. This procedure must be repeated every time the target device migrates from one cell to the next.
For the sourcing device to communicate with the target device in a wireless system, the sourcing device must send an IP packet addressed to the target device, i.e., must call the target device. This packet is routed to the local communications server which, in turn, uses a Mobile Network Location Protocol (MNLP) to reroute the packet to the MD-IS. The MD-IS then forwards the packet to the local communications server and, accordingly, the target device. Again, since all subsequent communication packets follow the same route, no direct connection is achieved between the local communications server to which the target device is attached and the sourcing device. Therefore, this method also is seen to suffer the same disadvantages previously discussed with respect to wireline systems. Furthermore, as a subscriber unit in a wireless system, e.g., cellular phone, typically relies upon batteries for power, the performance of this method is also seen to reduce battery life as the target subscriber unit needs to continually transmit to and re-register with the MDBS for each cell being passed through. Otherwise, communication packets from the sourcing device cannot be received.
As such, it is seen that a need currently exists for an improved target subscriber unit and method for establishing a communication path in a networked communications systems. Preferably, such a method and apparatus will be free of the drawbacks associated with the prior art, specifically, the drawbacks of causing a diminution of available bandwidths, the inefficiencies associated with re-addressing communication packets, and the unnecessary draining of batteries should batteries be used to power the portable target subscriber unit.